Re: [ecasound] GSM input and output

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Subject: Re: [ecasound] GSM input and output
From: Kai Vehmanen (k_AT_eca.cx)
Date: Fri Mar 22 2002 - 19:21:40 EET

On Fri, 22 Mar 2002, Armand Bendanan wrote:

> For the first point, I have a llok at the sources of ecasound and I see that
> the mp3 (and others) use an external command (mp123) in order to process the
> audio file. It seans that if I want to play gsm files, I have 3 possibility:
> - write a AUDIO_IO_DEVICE subclass for handling gsm

Nope, AUDIO_IO_DEVICE is reserved for realtime devices. Classes handling
non-realtime objects (like files) should derive from AUDIO_IO_BUFFERED or
straight from AUDIO_IO.

> - write a AUDIO_IO_FORKED_STREAM subclass and use some gsm (de)encoder

This is also a possibility, and quite likely the easiest solution.

> - find and use an ladspa plugin which handle directly the gsm.

This is also possible. Another option is to add support for audiofile
library that supports gsm files. There are quite a few generic libraries
available (libaudiofile, libsndfile, etc), but I don't know whether any of
them has gsm support.

And of course, using gsmlib directly is also an option
< http://www.pxh.de/fs/gsmlib/ >.

To make sure seeking works ok, you should implement
AUDIO_IO::seek_position(). See MP3FILE::seek_position() in
ecasound/libecasound/audioio-mp3.cpp:429.

> For the second point, I see that there was an option in ecasound (-y) which
> is available to specify the starting point of the audio file.
[....]
> But : if I put:
> ecasound -i minute.wav -y:2 -o /dev/dsp
[...]
> (eca-audio-objects) Set starting position for audio object "minute.wav": 2.00
> seconds.
[...]
> BUT, the audio file is started at the 11 second instead of the second one. I
> don't understand the way to specifiy the parameter of the -y option.

If this is true, it's a bug. -y should set the offset in second correctly.
What version of ecasound are you using? And what's the audio format of
'minute.wav'? 

-- 
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